The Chinese have known to use Magnetic needles for navigation on ships. Since then, the magnetic materials have been playing an increasingly important role in our lives. It's therefore necessary to understand the structure of such material.
Shapes of Magnet
The natural magnets i.e., iron ore were irregular in shape and weak. Later it was found that iron or steel acquired magnetic properties on rubbing with a magnet. Such magnets were called artificial or man-made magnet. These magnets have a desired shape and strength.
Properties of Magnet
a)
- A magnet attracts magnetic substances like iron, steel, cobalt and nickel towards it. The attraction is maximum at the ends called poles.
- A freely suspended magnet aligns itself in the N-S direction. The pole seeking the geographic north is the north pole (N) and the other is the south pole (S).(directive property)
- Like poles repel but unlike poles attract.
- Magnetic poles always exist in pairs.
b) Magnetic Dipole
The ordinary magnetic effects in materials are determined by atomic magnetism. On continuing to cut a magnet into its smallest bit, we reach the level of a single atom. This is a tiny current loop in which the current corresponds to the circulation of the electrons in the atom. To this atomic current we associate a magnetic dipole moment. This tiny bit cannot be further divided and hence the dipole is the smallest fundamental unit of magnetism.
A magnetic material can be regarded as a collection of magnetic dipole moments, each with a north and a south pole. Microscopically, each dipole is actually a current loop that cannot be split into individual poles.
